The present invention is directed to a socket for rotatably supporting a tool in a head housing of a dental handpiece which socket includes a catch means or device having at least one catch member which releasably locks a tool in the socket and is moved to an unlocking position by a thumb actuated purchase so that the tool may be removed from the socket.
Various systems are known for retaining or chucking dental tools in a socket of a dental handpiece. Thus, for tools which have cylindrical shanks, there are two known types of chucks, one is a friction chuck and the other is a screw chuck. An example of a friction collet is disclosed in U.S. Pat. No. 3,321,209. In this device, the collet has a sleeve which has been slotted to provide resilient tongues which are bent towards the center of the collet when in an idle state. When a tool shank is inserted, these resilient tongues are bent from their idle position and apply a gripping force to the shank. In order to remove the tool, the tool must usually be withdrawn or respectively ejected from the chucking device with the assistance of the special pressure or thrust tools. Insofar as it is carried out manually, the insertion and also the removal of the tool requires an exertion of great forces and requires special auxiliary devices such as drill ejector devices. Therefore the chucking and unchucking operation becomes relatively involved.
An example of the screw collet chuck is provided in U.S. Pat. No. 3,325,899. In this device, a separate auxiliary tool or wrench is required for securing and loosening the collet chuck.
In addition to tools which have cylindrical shanks, there are also tools which have an annular groove and a flattened portion adjacent or at the end of the cylindrical shank. The flattened portion can be brought into engagement with the dog in the hollow shaft of the socket to transmit torque therebetween. An example of a tool with an appropriate retaining device is disclosed for example in the earlier filed U.S. patent application Ser. No. 248,863 filed Mar. 30, 1981 and assigned to the assignee of the present application. In order to release the retaining element to enable an axial removal of the tool, a thumb actuatable purchase is tiltably seated at an upper end of the head housing which faces away from the neck part of the handpiece. In order to obtain a sufficient stroke to enable opening the retaining elements, it is necessary that the other end of the purchase which lies opposite the tilt position has sufficient movement. In two additional embodiments, which are disclosed in the above mentioned patent applications, the purchase, which is also loaded by a separate positioned spring, contains edge parts which are directed either towards the outside or respectively towards the inside and which coact with overlapping edge parts of the head housing to connect the purchase to the housing with the desired movement. Hereto, sufficient play must be provided between the head housing and the edge parts of the purchase so that the necessary stroke which is required for opening the retaining elements can be achieved.